pyinstaller tries to import electrum and its different submodules at build-time
during the "Analysis" phase. sys._GUI_QT_VERSION was not getting set there,
and the resulting exception was blocking pyinstaller from discovering that
gui/common_qt is being used.
at runtime:
```
$ ./dist/Electrum.app/Contents/MacOS/run_electrum
1.53 | E | daemon.Daemon | GUI raised exception: Exception('Error loading trustedcoin plugin: ModuleNotFoundError("No module named \'electrum.gui.common_qt\'")'). shutting down.
1.53 | E | __main__ | daemon.run_gui errored
Traceback (most recent call last):
File "electrum/plugin.py", line 135, in load_plugin
spec.loader.exec_module(module)
File "<frozen importlib._bootstrap_external>", line 883, in exec_module
File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
File "/Users/vagrant/electrum/dist/Electrum.app/Contents/MacOS/electrum/plugins/trustedcoin/qt.py", line 51, in <module>
from .common_qt import TrustedcoinPluginQObject
File "/Users/vagrant/electrum/dist/Electrum.app/Contents/MacOS/electrum/plugins/trustedcoin/common_qt.py", line 16, in <module>
from electrum.gui.common_qt.plugins import PluginQObject
ModuleNotFoundError: No module named 'electrum.gui.common_qt'
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "run_electrum", line 456, in handle_cmd
d.run_gui()
File "electrum/daemon.py", line 617, in run_gui
self.gui_object = gui.ElectrumGui(config=self.config, daemon=self, plugins=self._plugins)
File "electrum/util.py", line 473, in do_profile
o = func(*args, **kw_args)
File "electrum/gui/qt/__init__.py", line 153, in __init__
self.plugins.load_plugin('trustedcoin')
File "electrum/plugin.py", line 138, in load_plugin
raise Exception(f"Error loading {name} plugin: {repr(e)}") from e
Exception: Error loading trustedcoin plugin: ModuleNotFoundError("No module named 'electrum.gui.common_qt'")
```
